This invention relates to a magnetic tape transport system, more particularly a vacuum column type magnetic tape transport system utilizing a vacuum column as tape buffer means.
With recent advance of computer systems it becomes desirable to miniaturize various component parts so that an effort has been made to also miniaturize the magnetic tape transport system, which is a peripheral equipment of the computer system.
FIG. 1 shows one example of the magnetic tape transport system which has been developed to satisfy such requirement. This transport system is disclosed, for example in Japanese laid open Utility Model specification No. 137,510 of 1974.
The magnetic tape transport 10 shown in FIG. 1 comprises a supply or file reel 11, a take up or fixed reel 12 which are disposed in the vertical direction, a first vacuum column 13 disposed to the right of the reels with its upper end opened, and a second vacuum column 14 with its lower end opened. First and second auxiliary vacuum columns 15 and 16 are disposed near the openings of the first and second vacuum columns 13 and 14. The vacuum column 14 adjacent the reels 11 and 12 is provided with sliding guide members 17.sub.1 .about.17.sub.6, a magnetic head assembly 18, a capstan 19, and tape guides 20 and 21 which are arranged to form a path for the magnetic tape. There are also provided guide rollers 23, 24, 25 and 26, usually in the form of air bearings.
When automatically threading a magnetic tape 28 from the supply reel 11 to the take up reel 12, the magnetic tape payed out from the supply reel 11 passes between guide members 17.sub.1 and 17.sub.2, between guide member 17.sub.3 an tape guide 20 in front of the magnetic head assembly 18, and between guide member 17.sub.5 and tape guide 21, and then taken up by the take up reel 12. Thereafter, the vacuum column 13 is actuated to pull the magnetic tape toward the vacuum column 13 from between rollers 23 and 24 as shown in FIG. 1. The vacuum column 14 is also actuated to bring the magnetic tape to the state shown in FIG. 1.
With this construction, however, since the distance between the tape and the opening of the vacuum column 13 is large, it is not easy to pull the magnetic tape 28 toward the vacuum column 13. Moreover, as the distance between the vacuum column 13 and the capstan 19 is large and since guide rollers 24 and 25 are provided therebetween, the moment of inertia during operation, starting and stopping, the tension between a source of tension and a source of drive varies greatly, especially at the time of repeating start and stop and forward and reverse runnings in a short period. This causes poor contact of the magnetic tape 28 against the magnetic head thus rendering impossible satisfactory reading and writing. Moreover, since the direction of running of the magnetic tape 28 is changed twice by guide rollers 24 and 25, the decrease in the tension force applied to the magnetic tape 28 at these points can not be neglected.